生物醫(yī)學(xué)測量與儀器-wenkub
2023-01-19 14:17:55 本頁面
【正文】 —— 染料稀釋法 阻抗法 成像法：超聲、磁共振 心輸出量測量 HRSVCO ?? 連續(xù)輸注指示劑 —— 稀釋法 二、指示劑稀釋法 CdtdmdtdVF???/① When a given quantity m0 of an indicator is added to a volume V, the resulting concentration C of the indicator is given by C=m0/V. ② When an additional quantity m of indicator is then added, the incremental increase in concentration is △ C=m/V. ③ When the fluid volume in the measurement space is continuously removed and replaced, then in order to maintain a fixed change in concentration, the clinician must continuously add a fixed quantity of indicator per unit time .That is △ C=(dm/dt)/(dV/dt) Fick Technique（費克技術(shù)） va CCdtdmF??/F = blood flow, L/min dm/dt = consumption of O2, mL/min Ca = arterial concentration of O2, mL/L Cv = venous concentration of O2, mL/L Attention: ① In the Fick method, the indicator is O2. ② We cannot accurately measure Cv in the right atrium. We must measure it in the pulmonary artery after it has been mixed by the pumping action of the right ventricle. ③ We can measure the concentration of the oxygenated blood Ca in any artery. Thermodilution（熱稀釋法） TcqFbb ???q = rate of heat added, W ρb = density of the blood, kg/m3 cb = specific heat of the blood, J/ △ T = temperature change, K ?The best promise is to inject the heart into the right atrium and— after the heat has been mixed with normal blood in the right ventricle — to sample the resulting mixture in the pulmonary artery. 快速輸注指示劑稀釋法 ① An increment of blood of volume dV passes the sampling site in time dt. ② The quantity of indicator dm contained in dV is the concentration C(t) times the incremental volume. Hence dVtCdm )(?③ Dividing by dt, we obtain dtdVtCdtdm /)(/ ?④ But dV/dt=Qi, the instantaneous flow, therefore dttCQdm i )(?⑤ Integrating over time through t1, when the bolus has passed the downstream sampling point ,we obtain ?? 10 )(t i dttCQm⑥ Minor variations in the instantaneous flow Qi produced by the heartbeat are smoothed out by the mixing of the bolus and the blood within the heart chambers and the lungs. Thus we can obtain the average flow Q from ??10)(tdttCmQ? 熱稀釋法是較常用的心輸出量監(jiān)護法。心輸出量可由 StewartHamilton方程確定： ? 上式中 關(guān)的常數(shù)， b0是單位換算系數(shù)，上式中取 60， CT是指示劑在導(dǎo)管中升溫有關(guān)的無單位系數(shù)，對不同的導(dǎo)管，供應(yīng)商提供此參數(shù)， Vi和 Ti是冷生理鹽水的注入量（升）和溫度（ ℃ ）， Tb是注入冷生理鹽水前的血液溫度（ ℃ ）， Tb’ 是注入后在測溫點的血液溫度。 生物聲測量 心音 心音： 當(dāng)心臟跳動時由于心肌收縮、瓣膜關(guān)閉和血液沖擊的振動而產(chǎn)生的聲音。 第二心音 主動脈和肺動脈中的血流減速、回流及半月瓣關(guān)閉有關(guān)的低頻振動；半月形瓣膜把血液放進全身和肺動脈的循環(huán)系統(tǒng)。第三心音超前于心房收縮，此時心室松弛，所以是一種低頻、低幅值的振動，在小孩和一些年輕人中聽到。 （ 3） 主動脈瓣聽
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